An electronic rhythm generator particularly suitable for integrated circuitry

ABSTRACT

An electronic circuit for electrically simulating the sound of a plurality of rhythm instruments being played in any one of a plurality of different rhythmic patterns. The rhythmic patterns are generated by a clock pulse generator, a frequency divider, and a logic circuit which cooperate to produce pulses in rhythmic patterns which are characteristic of several different types of music. These pulses are applied to the plurality of keyed audio circuits which each produce a characteristic burst of output signals that simulate the audible output of a corresponding rhythm instrument. The keyed audio circuits include an audio oscillator, and means for repetitively coupling audio signals to the filter circuits in short bursts in synchronism with the rhythmic pulse patterns. The logic circuits, audio circuits, pulse switching circuits, and overall circuit configuration are arranged for maximum utilization of integrated circuits, interchangeable subcircuits, and printed circuits.

United States Patent [72] Inventors Harold O. Schwartz Tonawanda; Peter E. Maher; John E. Holt, both of North Tonawanda, allot, N.Y.

[2!] Appl. Np. 827,234

[22] Filed May 23,1969

[45] Patented June 22, 1971 [73] Assignee Thewurlltzer Company Chicago, Ill.

1541 srrz rsoslc. saxmnssssasxsza PARTICULARLY SUITABLE FOR INTEGRATED CIRCUITRY 12 Claims, 17 Drawing Figs.

[52] U.S,Cl .1 84/1. 03, 84/ 1.26 [51] lnt.Cl G10h 5/00, GlOh l/02,G10f1/00 [50] Field otSeareh 84/101, l.03,1.08,1.1l,l.26

[56] References Cited UNITED STATES PATENTS 3,309,454 3/1967 Cutler et a1. 84/103 1 3,358,069 12/1967 Hearne 84/1.03

3,383,452 5/1968 Park et al.... 84/1.03

3,515,792 6/1970 Deutsch 84/ 1.03

Park 84/1 .03 3,358,068 12/1967 Campbell s a/1.01 3,482,027 12/1969 okam0tOetal..... 84/l.03 3,489,842 1/1970 Ayres 84/101 Primary Examiner--Milton O. Hirshfield Assistant ExaminerStanley J. Witkowski Attorney-Olson, Trexler, Wolters and Bushnell ABSTRACT: An electronic circuit for electrically simulating the sound of a plurality of rhythm instruments being played in any one of a plurality of different rhythmic patterns. The rhythmic patterns are generated by aclock pulse generator, a frequency divider, and a logic circuit which cooperate to produce pulses in rhythmic patterns which are characteristic of several different types of music. These pulses are applied to the plurality of keyed audio circuits which each produce a characteristic burst of output signals that simulate the audible output of a corresponding rhythm instrument. The keyed audio circuits include an audio oscillator, and means for repetitively coupling audio signals to the filter circuits in short bursts in synchronism with the rhythmic pulse patterns. The logic circuits, audio circuits, pulse switching circuits, and overall circuit configuration are arranged for maximum utilization of integrated circuits, interchangeable subcircuits, and printed circuits.

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ELECTRONIC Rnrgry ggusmroa BACKGROUND OF THE INVENTION This invention relates to the art of electrically simulating the sounds of a plurality of rhythm instruments being played in different rhythmic patterns. More particularly, this invention relates to electronic rhythm generators which can be used in combination with electronic organs or the like to provide a rhythm accompaniment for music played on the organ.

Electronic rhythm generators per se are old in the art and this inventionis directed to improvements in prior art electronic rhythm generators such as exemplifiedby U.S. Pat. No. 3,358,069, which was issued on Dec. 12, I967 to .l. H. Hearne for a Rhythm Device"; U.S. Pat. No. 3,383,452, which was issued on May 14, I968 to D. M. Park et al. for a Musical Instrument"; and U.S. Pat. No. 3,255,292, which was issued on June 7, I966 to D. M. Park for an Automatic Repetitive Rhythm Instrument." As disclosed in the above-noted prior art patents, rhythm generators have been devised in the past wherein the sounds of percussive rhythm instruments being played in any one of several different rhythmic patterns are simulated electrically through the use of pulse generator circuits, logic circuits, and audio circuits for simulating the sound of percussive rhythm instruments. In each of the above-noted U.S. patents, the basic sounds of different percussive rhythm instruments are simulated through the use of audio circuits which, when activated in short bursts, simulate the sound of corresponding percussive rhythm instruments such as drums, tom toms, temple blocks, wood blocks, claves, maracas, brushes, cymbals or the like. These audio circuits are sequentially activated in one of several different repetitive patterns corresponding to different rhythms such as the fox trot, samba, waltz, etc. These rhythms are produced by the combined action of a pulse generator circuit which generates pulses of different frequency, a logic circuit which combines the pulses in a plurality of different rhythmic patterns corresponding to standard musical rhythms, and means for selectively switching the audio circuits in accordance with any predetermined one of the rhythms in order to simulate the sound of percussive rhythm instruments being played in accordance with the desired rhythm.

The above-noted prior an electronic rhythm generators have been successful in their primary objective of simulating the desired sounds, but they have suffered from several shortcomings and the purpose of this invention is to provide a novel electronic rhythm generator in which such shortcomings are minimized. In particular, one shortcoming of the prior art devices relates to physical size. Electronic rhythm generators are used as auxiliary instruments in connection with electronic organs and it is therefore desirable for the generator to be packaged so as tosit on top of an electronic organ within easy reach of the musician's hands. Since electronic organs and pianos are customarily designed for compactness, a relatively large generator is not only inconvenient but also unsightly. Accordingly, one object of this invention is to provide an electronic rhythm generator which can be packaged in a relatively small housing that will be inconspicuous when used with a small electronic organ and which will fit in the limited space that is available on the top of the smallest electronic organ within easy reach of the musician s hand.

Another drawback of the prior art devices relates to cost of manufacture. The simulation of percussive instrument sounds by electronic means and the generation of such sounds according to a plurality of differently rhythmic patterns requires the use of a substantial number of relatively expensive electronic components and it is highly desirably to provide circuit configurations in which the overall cost of manufacture is as low as possible. Accordingly, another object of this invention is to provide a high quality electronic rhythm generator which is simpler and more economical than those heretofore known in the art.

Also, in any electronic circuit, the problem of reliability is a paramount consideration and it is a further object of this invention to provide an electronic rhythm generator which is more reliable than those heretofore known in the art.

Finally, since the electrical simulation of percussive musical sounds is necessarily approximate in nature, there is always room for improvement in the fidelity of tone generation and it is a further object of this invention to provide an improved audio circuit which better simulates the true sound of percussive rhythm instruments.

SUMMARY OF THE INVENTION In accordance with this invention, the above-noted objects are achieved by a novel circuit design that provides for maximum utilization of integrated circuits, interchangeable subcircuits, interchangeable components, and printed circuits. This invention provides a novel rhythm pulse generator and associated logic circuit that utilizes standard solid-state integrated circuit components such as employed in digital computers to reduce the size and cost of the pulse generator portions of the circuit and to improve their reliability. These objectives are achieved by means of a novel logical grouping of pulses into basic pulse groups which are subunits of the rhythms to be generated by the circuit. The basic pulse groups are formed by a plurality of multiple input gate circuits which are substantially identical in circuit configuration except for their input and output connections. The basic pulse groups are then combined in various combinations with other pulses by a plurality of single input gate circuits which, when activated, apply a corresponding pulse or pulse group as the trigger input to a corresponding audio circuit. The single input gate circuits are activated in groups which, when activated simultaneously, will produce a combined output that provides a corresponding overall rhythm pattern. Different rhythms are selected by selector switch for activating any desired one of the single input gate circuit groups. In accordance with this invention, it has been found that the above-noted circuit arrangement simplifies the logic circuit and substantially reduces its cost.

The invention further provides for the use of integrated circuits, printed circuits, and the use of interchangeable subcircuit units not only in the pulse generator portion of the circuit but also in the audio portion'of the circuit so as to provide further economies in the cost of manufacture and further improvements in reliability. In addition, a novel audio circuit is provided for improving the quality of the audio output and for reducing the cost of the audio portion of the circuit. The audio circuit includes a master audio oscillator, a frequency divider for deriving lower audio frequencies therefrom, a group of audio filter circuits which, when energized by an appropriate audio frequency, simulate the output of a corresponding rhythm instrument, and a group of audio keying circuits for gating audio signals into the audio filter circuits in synchronism with the pulse output pattern of the pulse generator portions of the circuit. The master audio oscillator and frequency divider operate continuously and the audio signals are switched in the desired rhythmic pattern at the input of the audio filter circuits by the audio keying circuits. In accordance with this invention, it has been found that this particular audio circuit configuration simplifies the circuit, improves its fidelity, and further reduces the cost of manufacture.

With regard to physical packaging of the circuit, additional economies are achieved by mounting all of the logic circuit components on one printed circuit board and all of the audio circuit components on another. The assembly of these printed circuit boards is facilitated by the numerous interchangeable circuits that are employed both in the logic circuit and in the audio circuit.

The more detailed aspects of the invention will be described below with reference to the attached drawings, which show one illustrative embodiment of the invention.

DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of an electronic organ with one illustrative embodiment of the invention placed on top of the organ.

FIG. 2 is a perspective view of the embodiment of the invention shown in FIG. 1.

FIG. 3 is a block diagram illustrating the electrical connection between the rhythm generator of FIG. 2 and the amplifier and loud speaker system of the organ that it is used in combination with.

FIG. 4 is a block diagram of the electrical circuit of the rhythm generator of FIG. 2.

FIG. 5 is a set of waveforms illustrating the operation of the pulse generator portions of the circuit shown in FIG. 4.

FIG. 6 is a chart showing logical groupings of pulses used in the logic portions of the circuit shown in FIG. 4.

FIG. 7 is a block diagram of a typical flip-flop employed in the pulse generator circuitry of FIG. 4.

FIG. 8 is a schematic circuit diagram of a typical multiple input gate circuit employed in the pulse generator circuitry of FIG. 4.

FIG. 9 is a schematic circuit diagram of a group of typical single input gate circuits employed in the pulse generator circuitry of FIG. 4. 1

FIG. 10 is a schematic circuit diagram of a typical pulse amplifier, audio keying circuit, and audio filter circuit employed in the audio circuitry of FIG. 4. I

FIG. 11 is a chart which, in combination with the chart of FIG. 6, illustrates the logical combination of pulses and pulse groups that define the particular rhythmic patterns used in this embodiment of the invention.

FIGS. 12 and 12A are a complete schematic diagram for the audio portions of the circuitry in FIG. 4.

FIG. 12B shows the physical appearance of a printed circuit board on which the audio circuit shown in FIGS. 12 and 12A is mounted.

FIGS. 13 and 13 A are a complete schematic diagram for the logic portions of the circuitry in FIG. 4.

And FIG. 138 shows the physical appearance of a printed circuit board on which the logic circuit shown in FIGS. 13 and 13A is mounted.

DETAILED DESCRIPTION FIG. 1 shows one illustrative electronic rhythm generator of this invention sitting on top of an electronic organ. As can be seen in the drawing, the electronic rhythm generator 20 is contained in a relatively small package which sits unobtrusively on top of the electronic organ in the relatively limited area of free space that is available on top of the organ within easy reach of the musician s hands.

FIG. 2 shows the front panel controls that are available on this particular embodiment of the invention. These controls include projecting tabs which can be pressed to simulate the sound of a drum, brush, snare, block, or cymbal. Each of the projecting tabs shown beneath the corresponding rhythm instrument label will, when pressed, close a momentary contact switch to produce an output sound corresponding to one beat of the corresponding rhythm instnrment. The front panel controls also include selector switches for automatically, repetitively actuating the audio circuits to simulate the sound of these percussive instruments being played in any one of several rhythmic patterns including a waltz rhythm. Latin rhythm, fox trot rhythm, teen rhythm, and march rhythm. The front panel controls further include an off-on switch and volume control and a tempo adjustment for varying the tempo of the automatic rhythms.

This particular embodiment of the invention utilizes the amplifier and speaker system of the electronic organ as indicated in FIG. 3, where the audio output of electronic rhythm generator 20 is shown being applied to the organ amplifier 21 and loud speaker system 22. It will be understood by those skilled in the art, however, that other embodiments of the invention may be designed which have their own separate amplifier and speaker system if it is desirable for the electronic rhythm generator to be used independently.

FIG. 4 is an overall block diagram of the electrical circuitry for this particular embodiment of the invention. The audio output signals which simulate the sound of the percussive instruments are developed by a plurality of audio filter circuits 23 through 27 each of which is operable, when energized by an appropriate burst of audio' input signals, to produce audio output signals that simulate the audible sound of a corresponding percussive instrument.

Each of the audio filter circuits has coupled to its input a corresponding audio keying circuit 29 through 34. The keying circuits receive an audio input signal on one input and apply the audio input signal to the corresponding filter circuit when activated by an input pulse applied to another input. The audio input for the various pulse circuits is provided by an audio frequency generator system including a noise generator 35, which generates random audio frequencies, and a master audio oscillator system that generates different single frequencies to be applied to the appropriate filter circuits. The master audio oscillator is not shown in detail in FIG. 4 but is rather symbolized by three different audio frequency sources 36, 37, and 38 which apply frequencies of I04HZ, 208HZ, 832I-IZ to the drum keying circuit, snare drum keying circuit, and block keying circuit respectively.

The pulse input to the audio keying circuits 29 through 34 is applied via a group of pulse amplifiers 40 through 44. Each of these pulse amplifiers can be triggered independently by means of corresponding manual switches 45 through 49, which are actuated by the front panel tabs, or by pulses which are generated in the pulse generator circuit. The input jacks for the pulse generator inputs are indicated by the square boxes below the switches 45 through 49, each of the boxes being marked with an abbreviation for the corresponding instrument.

The automatic pulse sequences which are applied to the inputs of the pulse amplifiers 40 through 44 are generated by a clock oscillator 50, a frequency divider circuit comprising a first divider unit 51 which divides the clock frequency by three and a pair of frequency divider units 52 and 53, each of which contains two frequency dividing sections that divide the frequency by two. The outputs of frequency dividers 51, 52, and 53 are shown in the chart of FIG. 5, where each wave form on the chart is designated by the same capital letter designation as is used to indicate the various outputs of the frequency divider in FIG. 4. In other words, the waveform A shown in FIG. 5 corresponds to the output labeled A in FIG. 4, etc. FIG. 5 shows one full counting cycle for the clock oscillator and frequency dividers. The basic count unit is taken to be 48 clock pulses per cycle, this number being chosen becauseit can be divided by both three and by four so as to produce the required integral relation of beats used in differing musical rhythms.

The output pulse trains of the frequency divider circuits 51 through 53 are applied to a plurality of logical gates that are so connected as to produce counting sequences which define a waltz, Latin rhythm, fox trot rhythm, teen rhythm or march rhythm. The logical gates include .multiple input gates such as illustrated by circuit unit 54 and single input gates such as illustrated by circuit unit 55. Gate circuits 54 and 55 are shown with the appropriate input and output connections for generating the teen" rhythm used in this embodiment of the invention. It should be understood, however, that additional logic circuits similar to circuits 54 and 55 are required to produce all of the rhythms used in this embodiment of the invention as will be explained in detail later.

Before discussing the action of logic circuit 54 and 55 in detail, however, the general principles underlying the particular combinations of pulses used in accordance with this invention will first be described in connection with the waveform chart shown in FIG. 5 and the pulse charts shown in FIGS. 6 and 11. FIG. 6 shows a novel grouping of basic pulse patterns that are used in accordance with this invention to simplify the logical circuit and to allow the smallest number of common logical circuit elements to be used in the invention. Referring to FIG. 6, the symbol encircled on the left in the chart is a symbol for the combination of pulses indicated by the pulse numbers on the right, which refer to pulse periods in the basic clock pulse cycle of 48 pulses. In other words, the pulse group symbolized by three is the pulse group comprising the first, thirteenth, twenty-fifth, and thirty-seventh clock pulse in each cycle of 48 clock pulses. Likewise, the pulse group symbolized by four-twelfths is the pulse group comprising the 19th and 43rd clock pulses of a 48 pulse cycle. All of the basic pulse groups shown in the charts are repeated with every complete cycle of 48 clock pulses.

The basic pulse groups shown in FIG. 6 are combined as shown in FIG. 11 to produce the basic rhythms used in this embodiment of the invention. The chart of FIG. 11 indicates the pulse groups that are applied to the input of the corresponding percussive instrument channels to produce the various rhythm patterns. Thus, for example, the fox trot rhythm is generated by applying the pulse group three to the bass drum and cymbal and applying the pulse groups eight-elevenths and four to the brush. The other rhythms are generated in the same fashion by other combinations of the pulse groups as indicated in the chart. The rhythms themselves are not new but the basic pulse groupings illustrated in FIG. 6 which are combined to produce the overall rhythms are new and do lead to a simplification of the logic circuit.

The particular logical inputs for multiple input gate circuit 54 to produce the teen rhythm are shown in FIG. 4 and the detailed circuit for the gate circuit 54 is shown in FIG. 8. In this particular embodiment of the invention, the multiple input gates comprise NOR gates that are made from solid state materials in accordance with standard integrated circuit techniques. The single input gates 55, whose detailed circuit is shown in FIG. 9, also comprises solid-state circuits manufactured according to integrated circuit techniques. The single input gate circuits are transistor amplifiers that are .gated by switching their collector voltage off and on. This gating is done in groups of six where each of the amplifiers controls the input to one of the six audio frequency filters used in this embodiment of the invention. In FIG. 4, the collector voltage for the six amplifiers shown in circuit element 55 is switched on and off by means of switch 56 to simultaneously enable the amplifiers and apply the corresponding pulse rhythm to audio keying channels. The switching of the other single input gates for the remaining rhythms will be described later in connection with FIGS. 13 and 13A, which show the complete logic gating circuits for all of the rhythms.

FIG. shows a typical pulse amplifier, audio keying circuit, and audio filter circuit for simulating the rhythm instrument outputs. The filter circuit comprises a transistor 57 with an associated RC filter circuit which is designed to produce an output that simulates the sound of one of the percussive instruments when it is pulsed by a suitable audio frequency signal. The particular circuit values used and the detailed operation of the filter will not be described herein since they are well known in the prior art. The audio input is gated onto the base of transistor 57 through a pulse responsive switching circuit including diodes 58 and 59. Audio input signals are applied continuously to the cathode of diode 58, but diode 58 is normally back biased by a negative voltage level on the cathode and does not conduct until a positive voltage pulse is coupled to the circuit through diode 59. When such a pulse is applied through diode 59, the audio input applied to the cathode of diode 58 will be coupled through resistor 60 and capacitor 63 to the base of transistor 57 to produce a burst of output signals that simulate the characteristics of a desired percussive instrument. After a pulse has been applied through diode 59, the keying circuit will remain enabled for a time period which is determined by the RC charging time of capacitor 61, resistor 62, and diode 58.

The 'positive pulse input to diode 59 is provided by a pulse amplifier circuit comprising transistor 64 and its associated circuit components. The input pulse for the transistor 64 is applied to the base thereof from one of the single input gating circuits such as illustrated by circuit unit 55 in FIG. 4. Although the characteristics of the filter circuits differ in each of the filters 23 through 27 in FIG. 4, the keying circuits 29 through 34 all have the same circuit configuration as shown in FIG. 10, and the pulse amplifiers 40 through 44 have the same circuit configuration as shown in FIG. 10. This duplication of the same basic circuit provides a considerable saving in cost in that common parts and common circuit configurations are used which thereby reduces the procurement cost of the circuit components and simplifies the assembly techniques.

In the prior art electronic rhythm generators, the required audio signals were produced by keying a plurality of audio oscillators between an off condition and an on condition when their particular frequency was required for simulating a particular sound. In accordance with this invention, however, it has been found that a superior simulation of the desired sounds can be achieved by an audio oscillator system which operates continuously instead of being switched off and on. The switching of the audio signals to achieve the desired percussive effect is achieved by providing separate audio switching circuits at the input of each of the audio filter circuits as described above. Also, in accordance with this invention, the required audio frequency signals are derived from a single master audio oscillator in combination with a frequency divider system which divides the master oscillator frequency to produce lower frequency audio signals. The master audio oscillator and frequency divider system is illustrated in FIG. 12A. The master audio oscillator is a unijunction transistor relaxation oscillator which includes a unijunction transistor 28 and an associated RC feed back network arranged to provide continuous square wave oscillations at a relatively high audio frequency with respect to the audio frequencies involved in simulating the various percussive instruments. The circuit of the unijunction transistor oscillator will not be described in detail inasmuch as it is a known circuit configuration whose operation will be understood by those skilled in the art from the schematic. The output oscillations of the master audio oscillator are applied to a four-stage flip-flop counter comprising a pair of integrated circuits 65 and 66 each of which contains two J-K flip-flops such as illustrated in FIG. 7. The four flip-flops on integrated circuit cards 65 and 66 are coupled together in a standard binary counter configuration which serves as a frequency divider for dividing the frequency of the master oscillator by factors of 2, 4, 8, and 16 as will be readily understood by those skilled in the art. The appropriate stages of the divider circuit are used to provide the 832I-IZ, 208HZ, and 104l-IZ signals which are illustrated in FIG. 4 as being derived from symbolic generators 36, 37, and 38, and it will be understood by those skilled in the art that the generators 36, 37, and 38 constitute corresponding flip-flops in the binary counter circuit formed from integrated circuits 65 and 66.

FIGS. 12, 12A, and 128 show the detailed circuit and printed circuit mounting arrangement for the audio portion of the circuitry. Referring to FIG. 12A, the audio portion of the circuit can be located on its input side with respect to the overall block diagram of FIG. 4 by means of the instrument control switches 45 through 49 which are shown on both FIG. 4 and on FIG. 12. In FIG. 4 the switches 45 through 49 are shown as connected to blocks representing their respective pulse amplifiers while on FIG. 12 the detailed schematic for each pulse amplifier is shown. The detailed schematic circuits for the various keying circuits, filter circuits, and other circuits are shown in full schematic form in FIGS. 12 and 12A, but it will be understood by those skilled in the art that these circuits correspond to those which are shown in block diagram form in FIG. 4.

The circuit portion which is shown enclosed in the dashed lines on FIG. 12 and 12A is mounted on a single printed circuit board as shown in H6. 128. The power supply circuit,

which is shown in FIG. 12A, contains portions which are also mounted on the same printed circuit board. The power supply circuit will not, however, be described in detail inasmuch as it is 'a known regulated power supply circuit whose operation will be immediately apparent to those skilled in the art from the schematic drawing per se. The filter circuits, audio keying circuits, and pulse amplifier circuits shown in FIG. 12 have been previously described in connection with the typical circuits shown in FIG. 10.

It will be noted that in FIG. 12 all of the pulse amplifier circuits and keying circuits are similar in circuit configuration but that the keying circuit for the snare drum is modified slightly to receive a pulse train input from the snare roll oscillator which is identified as circuit element No. 39 in the overall block diagram of FIG. 4, and which comprises the unijunction transistor oscillator circuit identified as the "roll oscillator" in FIG. 12. This oscillator circuit will not be described in detail, since it comprises a known unijunction oscillator. It is believed sufficient to note that this oscillator circuit provides a relatively low frequency square wave pulse output that repetitively switches the snare drum keying circuit to simulate the roll of a snare drum when snare roll switch 46 is closed or when the associated input terminal is grounded by a signal from the logic circuitry.

It should also be noted that the noise generator which is identified as circuit element No. 35 in the overall block diagram of FIG. 4 comprises a diode noise source and transistor noise amplifier which are identified in FIG. 12 by the labels noise source" and noise amplifier. These two circuits will not be described in detail inasmuch as they comprise known circuits and the interaction of the noise source and noise amplifier in providing a source of audio noise for the brush, cymbal, and snare drum filter circuits will be readily apparent to those skilled in the art from the schematics per se.

FIGS. 13, 13A, and 138, show the detailed-circuit connections for the logic portion of the circuit and the physical mounting of the logic circuit elements on a common printed circuit card. Referring to FIGS. 13 and 13A, the integrated circuit cards labeled as lC-3, 4, and 9 each comprise dual JK flip-flops such as illustrated in FIG. 7, and these flip-flops are interconnected to form the frequency division circuit illustrated in the overall block diagram of FIG. 4. The integrated circuit card labeled lC-l4, which is shown as being interconnected between several contacts of the various frequency divider stages, comprises an amplifier circuit such as illustrated in FIG. 9 for amplifying the various feed back signals between the different flip-flop stages of the frequency divider circuit. It will be noted both in FIG. 13A and in the overall block diagram of FIG. 4 that the frequency divider flip-flops can be reset to zero by an optional foot switch so that the operator can control the starting time of the rhythm by depressing the foot switch to reset the flip-flop counter and then releasing the switch when he wishes the rhythm to begin.

The integrated circuit cards which are labeled as IC-Z, 5, 8, l0, and 13 in FIGS. 13 and 13A each comprise NOR gates such as illustrated in FIG. 8. The input to the various NOR gates are coupled from the frequency divider circuit in accordance with the pulse count logic shown in FIG. 6 to produce the corresponding basic pulse groups which are geometrical shapes used to designate the outputs from integrated circuit card lC-14, most of the inputs to the NOR gates are taken from the outputs of the amplifiers on the integrated circuit card 14. Several of the inputs to the NOR gates are, however, taken directly from the output of the corresponding flip-fiop for the purposes of balancing the load.

The integrated circuit cards which are identified in FIGS. 12 and 12A by the designations IC-l, 6, 7, l1, and 12 each constitute amplifier circuits such as disclosed in FIG. 9. The inputs to each of these amplifiers comprise combinations of the outputs from the NOR gate circuits and from the frequency divider flip-flop circuits taken in accordance with the combinations illustrated in FIG. 11, which combinations refer back to the basic pulse groups shown in FIG. 6. As explained previously, each group of amplifiers on one of the integrated circuit cards acts not only as an amplifier but also as a single input gating circuit for switching the corresponding pattern of pulses unto the input keying circuit of the various rhythm instrument simulation circuits. In the particular rhythms which are employed in this embodiment of the invention, several of the rhythmic patterns do not employ all of the available rhythm instruments, e.g. the waltz rhythm does not use the brush or the block or the snare roll, while the fox trot, teen, and march rhythms do not use the block, etc. These particular omissions will be noted in FIGS. 12 and 12A by the fact that some of the output terminals from integrated circuit cards IC-l, 6, 7, 11, and 12 are not connected to any of the rhythm instrument simulation channels.

Also, as noted earlier with respect to the switch 56, which is identified by the label teen in both the general block diagram of FIG. 4 and in FIG. 13, the collector voltage to all of the amplifiers on any one integrated circuit card is switchable by means of the front panel switches that select the desired rhythm to allow the appropriate combination of pulses to rhythm through into the rhythm instrument simulation channels. The function of switch 56 in activating the amplifiers that define the teen rhythm has been described above in connection with the general block diagram of FIG. 4. It will be unidentified at the outputs of the NOR gates by the same numbers used in the Chart of FIG. 6. The inputs to the NOR gates are identified by letter designations which refer both to the letter designations'used in specifying the various outputsof the frequency divider flip-flop circuit and also to the wave forms of those outputs as shown in FIG. 5. The geometrical shapes of the designations at the input to the various NOR gates designates the particular point in the flip-flop circuit from whichthe corresponding input is taken. It will be noted that several of the flip-flop outputs are available both at the output of the flip-flop itself and also at the output of a corresponding one of the amplifiers mounted on printed circuit card IC-l4. And, as can be seen by comparing the geometrical shape of the input designations to the NOR gates with the derstood by those skilled in the art that switches 67 through 70 (FIGS. 13 and 13A) perform the same function for the integrated circuit cards defining their corresponding rhythmic pattern. Switch 69, however, differs from the other switches in that it includes a single-pole-single-throw switch that is mechanically linked to the single-pole double-throw switch to alter the frequency of the clock oscillator for the march tempo by disconnecting the capacitor 71 from the clock oscillator circuit when the march tempo switch 69 is pressed. Capacitor 71 is normally connected in parallel with capacitor 72 in the clock oscillator circuit and the removal of the ground connection from capacitor 71 reduces the amount of capacitance connected to the emitter of unijunction transistor 73, thereby increasing its frequency of oscillation. The unijunction transistor oscillator circuit which comprises the clock oscillator is believed to be self-explanatory to those skilled in the art inasmuch as it constitutes a known circuit.

The potentiometer which controls the frequency of the clock oscillator circuit is mounted as a front panel control which is labeled tempo adjustfl The tempo lamp which is shown in FIG. 13A directly above the tempo adjustment potentiometer is also a front panel indicator. This lamp is driven by a transistor amplifier which is coupled to one of the amplifiers on integrated circuit card IC-Z. The tempo lamp is pulsed in accordance with the pulse sequence labeled as tempo pulse on the chart in FIG. 6 to provide a visual indication of the tempo for both adjustment purposes and for playing purposes. The flashing tempo lamp on the top of the organ console assists the musician in playing his organ music in synchronism with the rhythm accompaniment.

It should be noted in FIG. 13A that the logical inputs to integrated circuit card IC-l, which defines the waltz rhythm, is switched by diode AND gates 74 rather than being switched at the collector input to the integrated circuit card itself. The AND gates 74 are used instead of NOR gates because with the particular logical function involved diode gates are slightly more economical than transistor gates in terms of space and cost. The other logical functions are, however, more economically formed by means of the NOR gates. The inputs three, seven, and nine to the diode AND gates 74 are taken from the output of corresponding NOR gates on integrated circuit cards lC-8 and lC-Z. The AND gates 74 are switched by a voltage applied through waltz selector switch 70, and since the amplifiers on integrated circuit card lC-l are switched at their inputs, it is not necessary to switch their collector voltage.

FlG. 138 shows the mounting arrangement for mounting the logic circuit components shown in H68. 13 and 13A on a common printed circuit board. As will be seen, the integrated circuit cards, which are approximately actual size, are grouped in rows according to their function to facilitate the interconnections thereinbetween. The three integrated circuit which comprise the frequency divider (lC-3, 4, and 9) are grouped together in a row near the upper edge of the printed circuit board, while the integrated circuit lC-l4 containing the amplifiers for amplifying the flip-flop outputs is positioned directly below the integrated circuit cards containing these flip-flops. The integrated circuits comprising the NOR gates (lC-2, 5, 8, l0, and 13) are grouped together in a row in the center of the printed circuit board and the integrated circuit cards comprising the switched amplifiers (lC-l, 6, 7, H, and 12) are grouped together in a row on the bottom of the printed circuit board. The associated resistors, capacitors, and other circuit units are physically arranged for maximum convenience in wiring the circuit together. In considering the total amount of electrical circuitry contained on this one printed circuit board, it will be apparent that a substantial simplification of the circuit manufacturing process and a substantial reduction in volume of the final circuit are achieved in the electronic rhythm generator circuit of this invention.

All of the circuitry shown in the various schematics with the exception of the front panel switches and some of the power supply components are mounted on the two printed circuit cards shown in FIGS. 12B and 138. Moreover, there is a high incidence of common subcircuits and common components used on the boards which also makes a significant contribution to the reduction of cost not only in the procurement of parts but also in the problem of storing parts and assembling them on the printed circuit boards.

From the foregoing description it will be apparent that this invention provides an electronic rhythm generator which is significantly smaller in volume, more reliable in operation, and more economical in cost of manufacture than those heretofore known in the art. And although this invention has been illustrated with reference to one specific embodiment thereof, it should be understood that many specific modifications can be made in the disclosed circuits without departing from the basic teaching of this disclosure. For example, other rhythms can be added if desired to the particular rhythms which have been disclosed in this particular embodiment of the invention, and other rhythm instruments can be simulated if desired by adding more audio frequency channels. In addition, numerous detailed modifications can bemade in the individual flip-flop circuits, gate circuits, amplifier circuits, keying circuits, audio oscillator circuits, and filter circuits disclosed in this particular embodiment of the invention to adapt the invention for any particular application. Many such modifications will be readily apparent to those skilled in the art and it is to be understood that this invention includes all such modifications that fall within the scope of the following claims.

We claim:

I. An electronic rhythm generator for electrically simulating the sound of a plurality of rhythm instruments being played in a predetermined rhythmic pattern, said rhythm generator comprising a plurality of keyed audio circuits each operable when triggered by an input pulse to produce a characteristic burst of audio output signals that simulate the audible output of a corresponding rhythm instrument, a pulse generator circuit for producing pulses at a predetermined clock frequency, a frequency divider circuit coupled to the output of said pulse generator circuit for dividing the frequency of said pulses in accordance with a plurality of different integral ratios to produce a plurality of pulse trains that differ in frequency by characteristic integral ratios, a plurality of multiple input gate circuits coupled to the output of said frequency divider circuit for logically combining predetermined pulse trains to form a plurality of repetitive pulse groups, the input to each multiple input gate circuit being so connected as to produce a different pulse group at the output thereof, and each of said pulse groups being a subunit of one or more musical rhythm patterns, a plurality of single input gate circuits coupled to the outputs of said multiple input gate circuits, means coupling the outputs of said single input gate circuits to the trigger inputs of corresponding keyed audio circuits, and means for simultaneously activating predetermined combinations of said single input gate circuits to apply a characteristic repetitive rhythmic pattern of trigger input signals to said keyed audio circuits, thereby producing a corresponding repetitive sequence of electrical output signals from said keyed audio circuits to simulate the sound of a plurality of rhythm instruments being played in accordance with the said characteristic repetitive rhythmic pattern.

2. An electronic rhythm generator as defined in claim 1 wherein said single input gate circuits are associated together in a plurality of groups, the input to each group of single input gate circuits being connected to produce a different characteristic repetitive rhythmic pattern at the outputs thereof, and wherein said means for simultaneously activating predetermined combinations of said single input gate circuits comprises means for simultaneously activating any predetermined one of said groups of gate circuits to apply any one of a plurality of different characteristic repetitive rhythmic patterns to the trigger inputs of said keyed audio circuits, thereby electrically simulating the sound of said plurality of rhythm instruments being played in any one of a plurality of different rhythmic patterns.

3. An electronic rhythm generator as defined in claim 2 wherein each of said single input gate circuits comprises a transistor amplifier and wherein said means for activating said single input gate circuits comprises switch means for applying operating voltage to said transistor amplifiers.

4. An electronic rhythm generator as defined in claim 3 wherein said switch means for applying operating voltage to said transistor amplifiers comprises a plurality of switches each connected so as to simultaneously apply operating voltage to a different group of said transister amplifiers to couple a corresponding characteristic repetitive rhythmic pattern to the trigger inputs of said keyed audio circuits.

5. An electronic rhythm generator as defined in claim 4 wherein said frequency divider circuit comprises a plurality of substantially identical flip-flops coupled together in a counter circuit configuration, and wherein said multiple input gate circuits are substantially identical in circuit configuration except for the input and output connections thereto, and wherein said transistor amplifiers are substantially identical in circuit configuration except for the input and output connections thereto, and wherein said flip-flops, multiple input gate circuits, and transistor amplifiers all comprise solid state integrated circuits.

6. An electronic rhythm generator as defined in claim 5 wherein said flip-flops, gate circuits, amplifiers, and their associated circuit components are all mounted on a common printed circuit board.

7. An electronic rhythm generator as defined in claim 6 wherein said flip-flops are mounted substantially in a parallel row on said printed circuit board, and wherein said multiple input gate circuits are mounted in a second substantially parallel row adjacent to said flip-flops, and wherein said transistor amplifiers are mounted in a third substantially parallel row adjacent to said multiple input gate circuits but not to said flipflop'circuits. i

8. An electronic rhythm generator as defined in claim 2 wherein said frequency divider circuit produces an overall repetitive cycle of pulses in which the same pattern of pulses is repeated for each adjacent sequence of 48 clock pulses, and wherein the said repetitive pulse groups formed at the output of said multiple input gate circuits include the following repetitive pulse groups:

A. A first pulse group in which the first, seventh, thirteenth, nineteenth, twenty-fifth, thirty-first, thirty-seventh, and forty-third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

B. A second pulse group in which the first, thirteenth, twenty-fifth, and thirty-seventh pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

C. A third pulse group in which the seventh, nineteenth, thirty-first, and forty-third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

D. A fourth pulse group in which the fifth, seventeenth, twenty-ninth, and forty-first pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

E. A fifth pulse group in which the ninth, twenty-first, thirtythird, and forty-fifth pulses of the basic 48 pulse clock cycle are'present and all of the other pulses thereof are absent;

F. A sixth pulse group in which the nineteenth and forty third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

G. A seventh pulse group in which the eleventh, twentythird, thirty-fifth, and forty-seventh pulse of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

H. An eighth pulse group in which the first and twenty-fifth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

l. A ninth pulse group in which the tenth and thirty-fourth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

1. A tenth pulse group in which the twentysecond and forty-sixth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent;

K. An eleventh pulse group in which the forty-sixth, fortyseventh and forty-eighth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; and

, L. A twelfth pulse group in which the first, fourth, seventh, tenth, thirteenth, sixteenth, nineteenth, twenty-second, twenty-fifth, twenty-eighth, thirty-first, thirty-fourth, thirty-seventh, fortieth, forty-third and forty-sixth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent.

9. In an electronic rhythm generator for electrically simulating the sound of a plurality of rhythm instruments and including a plurality of keyed audio circuits each operable when triggered by an input pulseto simulate the audible output of a corresponding rhythm instrument, the improvement wherein said keyed audio circuits comprise a plurality of audio filter circuits each operable when energized by appropriate audio input signals to produce audio output signals that simulate the audible output of a corresponding rhythm instrument, an audio frequency oscillator for producing an audio signal, an audio frequency divider coupled to said audio frequency oscillater for deriving lower frequency audio signals therefrom, and means for coupling said audio signals to the inputs of corresponding audio filter circuits to produce audio output signals that simulate the audible output of corresponding rhythm instruments, said audio frequency oscillator and frequency divider operating continuously when said electronic rhythm generator is in operation and further comprising means for repetitively coupling said audio signals to said audio filter circuits in relatively shortbursts in accordance with a predetermined rhythmic patternj,'said means for repetitively coupling said audio signalsto said audio filter circuits in relatively short bursts comprisingpulse generator means for producing a predetermined'rhythrnic pattern of electrical pulses, a plurality of pulse actuated audio keying circuits each coupled to the input of a corresponding audio filter circuit, said audio signals being coupled to the audio input of corresponding audio keying circuits, each audio keying circuit being operable when triggered by an input pulse to apply said audio signals to the corresponding audio filter circuit for a relatively short period of time, and means for coupling said pulses from said pulse generator means to said audio keying circuits to trigger the audio keying circuits in accordance with said predetermined rhythmic pattern.

10. The improvement defined in claim 9 wherein said means for coupling said pulses from said pulse generator means to said audio keying circuits comprises a plurality of trigger input amplifiers each coupled between said pulse generator and a corresponding one of said audio keying circuits.

11. The improvement defined in claim 10, and further comprising an audio frequency noise generator for producing random frequency audio signals and means for coupling said random frequency audio signals to the audio input of at least one of said audio keying circuits.

12. The improvement defined in claim 11, wherein said audio frequency oscillator, frequency divider, noise generator, keying circuits, filter circuits, and trigger input amplifiers are all mounted on a common printed circuit board.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 91 Dated June 22 197].

lnventol-(s) Harold 0. Schwartz, Peter E. Maher and John E. Holt It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the abstract, line 11, after "oscillator" insert the phrase --and audio frequency divider, a plurality of audio filter circuits,-

Column 8 line 35, before "throu h" change "rh thm" to --pass- Signed and sealed this 18th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOITSCHALK Acting Commissionerof Patents USCOMM-DC 60376-P69 u s cnvzmmim PRINTING OFFICE was 0-366-13:

! FORM PO-IOSO (10-69] 

1. An electronic rhythm generator for electrically simulating the sound of a plurality Of rhythm instruments being played in a predetermined rhythmic pattern, said rhythm generator comprising a plurality of keyed audio circuits each operable when triggered by an input pulse to produce a characteristic burst of audio output signals that simulate the audible output of a corresponding rhythm instrument, a pulse generator circuit for producing pulses at a predetermined clock frequency, a frequency divider circuit coupled to the output of said pulse generator circuit for dividing the frequency of said pulses in accordance with a plurality of different integral ratios to produce a plurality of pulse trains that differ in frequency by characteristic integral ratios, a plurality of multiple input gate circuits coupled to the output of said frequency divider circuit for logically combining predetermined pulse trains to form a plurality of repetitive pulse groups, the input to each multiple input gate circuit being so connected as to produce a different pulse group at the output thereof, and each of said pulse groups being a subunit of one or more musical rhythm patterns, a plurality of single input gate circuits coupled to the outputs of said multiple input gate circuits, means coupling the outputs of said single input gate circuits to the trigger inputs of corresponding keyed audio circuits, and means for simultaneously activating predetermined combinations of said single input gate circuits to apply a characteristic repetitive rhythmic pattern of trigger input signals to said keyed audio circuits, thereby producing a corresponding repetitive sequence of electrical output signals from said keyed audio circuits to simulate the sound of a plurality of rhythm instruments being played in accordance with the said characteristic repetitive rhythmic pattern.
 2. An electronic rhythm generator as defined in claim 1 wherein said single input gate circuits are associated together in a plurality of groups, the input to each group of single input gate circuits being connected to produce a different characteristic repetitive rhythmic pattern at the outputs thereof, and wherein said means for simultaneously activating predetermined combinations of said single input gate circuits comprises means for simultaneously activating any predetermined one of said groups of gate circuits to apply any one of a plurality of different characteristic repetitive rhythmic patterns to the trigger inputs of said keyed audio circuits, thereby electrically simulating the sound of said plurality of rhythm instruments being played in any one of a plurality of different rhythmic patterns.
 3. An electronic rhythm generator as defined in claim 2 wherein each of said single input gate circuits comprises a transistor amplifier and wherein said means for activating said single input gate circuits comprises switch means for applying operating voltage to said transistor amplifiers.
 4. An electronic rhythm generator as defined in claim 3 wherein said switch means for applying operating voltage to said transistor amplifiers comprises a plurality of switches each connected so as to simultaneously apply operating voltage to a different group of said transister amplifiers to couple a corresponding characteristic repetitive rhythmic pattern to the trigger inputs of said keyed audio circuits.
 5. An electronic rhythm generator as defined in claim 4 wherein said frequency divider circuit comprises a plurality of substantially identical flip-flops coupled together in a counter circuit configuration, and wherein said multiple input gate circuits are substantially identical in circuit configuration except for the input and output connections thereto, and wherein said transistor amplifiers are substantially identical in circuit configuration except for the input and output connections thereto, and wherein said flip-flops, multiple input gate circuits, and transistor amplifiers all comprise solid state integrated circuits.
 6. An electronic rhythm generator as defined in claim 5 wherein said flip-flops, gate circUits, amplifiers, and their associated circuit components are all mounted on a common printed circuit board.
 7. An electronic rhythm generator as defined in claim 6 wherein said flip-flops are mounted substantially in a parallel row on said printed circuit board, and wherein said multiple input gate circuits are mounted in a second substantially parallel row adjacent to said flip-flops, and wherein said transistor amplifiers are mounted in a third substantially parallel row adjacent to said multiple input gate circuits but not to said flip-flop circuits.
 8. An electronic rhythm generator as defined in claim 2 wherein said frequency divider circuit produces an overall repetitive cycle of pulses in which the same pattern of pulses is repeated for each adjacent sequence of 48 clock pulses, and wherein the said repetitive pulse groups formed at the output of said multiple input gate circuits include the following repetitive pulse groups: A. A first pulse group in which the first, seventh, thirteenth, nineteenth, twenty-fifth, thirty-first, thirty-seventh, and forty-third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; B. A second pulse group in which the first, thirteenth, twenty-fifth, and thirty-seventh pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; C. A third pulse group in which the seventh, nineteenth, thirty-first, and forty-third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; D. A fourth pulse group in which the fifth, seventeenth, twenty-ninth, and forty-first pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; E. A fifth pulse group in which the ninth, twenty-first, thirty-third, and forty-fifth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; F. A sixth pulse group in which the nineteenth and forty-third pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; G. A seventh pulse group in which the eleventh, twenty-third, thirty-fifth, and forty-seventh pulse of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; H. An eighth pulse group in which the first and twenty-fifth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; I. A ninth pulse group in which the tenth and thirty-fourth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; J. A tenth pulse group in which the twenty-second and forty-sixth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; K. An eleventh pulse group in which the forty-sixth, forty-seventh and forty-eighth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent; and L. A twelfth pulse group in which the first, fourth, seventh, tenth, thirteenth, sixteenth, nineteenth, twenty-second, twenty-fifth, twenty-eighth, thirty-first, thirty-fourth, thirty-seventh, fortieth, forty-third and forty-sixth pulses of the basic 48 pulse clock cycle are present and all of the other pulses thereof are absent.
 9. In an electronic rhythm generator for electrically simulating the sound of a plurality of rhythm instruments and including a plurality of keyed audio circuits each operable when triggered by an input pulse to simulate the audible output of a corresponding rhythm instrument, the improvement wherein said keyed audio circuits comprise a plurality of audio filter circuits each operable when energized by appropriate audio input signals to produce audio output signals that simulate the audible output of a corresponding rhythm instrument, an audio frequency oscIllator for producing an audio signal, an audio frequency divider coupled to said audio frequency oscillator for deriving lower frequency audio signals therefrom, and means for coupling said audio signals to the inputs of corresponding audio filter circuits to produce audio output signals that simulate the audible output of corresponding rhythm instruments, said audio frequency oscillator and frequency divider operating continuously when said electronic rhythm generator is in operation and further comprising means for repetitively coupling said audio signals to said audio filter circuits in relatively short bursts in accordance with a predetermined rhythmic pattern, said means for repetitively coupling said audio signals to said audio filter circuits in relatively short bursts comprising pulse generator means for producing a predetermined rhythmic pattern of electrical pulses, a plurality of pulse actuated audio keying circuits each coupled to the input of a corresponding audio filter circuit, said audio signals being coupled to the audio input of corresponding audio keying circuits, each audio keying circuit being operable when triggered by an input pulse to apply said audio signals to the corresponding audio filter circuit for a relatively short period of time, and means for coupling said pulses from said pulse generator means to said audio keying circuits to trigger the audio keying circuits in accordance with said predetermined rhythmic pattern.
 10. The improvement defined in claim 9 wherein said means for coupling said pulses from said pulse generator means to said audio keying circuits comprises a plurality of trigger input amplifiers each coupled between said pulse generator and a corresponding one of said audio keying circuits.
 11. The improvement defined in claim 10, and further comprising an audio frequency noise generator for producing random frequency audio signals and means for coupling said random frequency audio signals to the audio input of at least one of said audio keying circuits.
 12. The improvement defined in claim 11, wherein said audio frequency oscillator, frequency divider, noise generator, keying circuits, filter circuits, and trigger input amplifiers are all mounted on a common printed circuit board. 